This invention relates to a fluid filter, particularly of the type used to filter engine oil in an automotive vehicle, concerns an improved anti-drainback and relief valve therefor.
Fluid filters, particularly those used to filter engine oil in an automotive vehicle, are commonly provided with an anti-drainback valve, to trap fluid in the filter and prevent it leaking out of the filter when the vehicle engine is turned off, and are also provided with a bypass valve, which is normally closed, but which opens to permit direct communication between the filter inlet and outlet when the filter becomes clogged, so that the vehicle engine will not be starved for lubrication. One type of such a combined anti-drainback and bypass valve known to the prior art is disclosed in my prior U.S. Pat. No. 3,567,022. However, this valve, although it has been quite successful, has proved to be relatively expensive to manufacture, because of the large number of separate parts required. Another type of combined anti-drainback and bypass valve used in an automotive filter is disclosed in my prior art U.S. Pat. No. 3,231,089. However, this valve is made entirely of rubber, and it has proven difficult to attain opening and closing of the valve at the very close pressure ranges required over the relatively large temperature variations in which automotive vehicles are often operated.
A fluid filter made pursuant to the present invention avoids most of the problems inherent with the prior art assemblies discussed hereinabove. The present invention proposes an anti-drainback/relief valve for an oil filter which consists of only a single, relatively easily manufactured part. The part includes a spring metal inner member encapsulated in a rubber compound. Since the spring rate of the spring member is independent of ambient temperature, the opening and closing of the relief and anti-drainback can be controlled to within a relatively small pressure range independent of the relatively large variations of ambient temperature in which modern vehicles are operated.